Process for stretching a cable of polyester threads

ABSTRACT

Improved stretching process for polyester cables wherein the penultimate roller of an inlet roller mechanism is immersed in a bath maintained at a temperature of 40*-65*C and the last roller of the mechanism is higher than the penultimate roller and is maintained at a temperature 3*-18*C higher than the immersion bath. Further the angle between vertical and the cable as it rises to the last roller is less than 55*. The resultant cables have a low percentage unstretched fibers and, as a consequence, have a low percentage dyeing defects.

United States Patent 1191 1111 3,894,135 Riggert et al. July 8, 1975 [54] PROCESS FOR STRETCHING A CABLE OF 2,918,346 12/1959 Paulsen 264/210 F P LYESTER THREADS 3,077,004 2/1963 Mummery.... 264/290 T 3,259,681 7/1966 Bull et a1 264/290 T [75] Inventors: Karlheinz Riggert, Dornholzhausen; 3,557,273 1 1971 Bergwerk 264/290 T Willy Zahn, l-leusenstamm; 3,567,817 3/1971 Spiller 264/290 T Bernhard Jantzen; Rolf Sander, 3,651,198 3/ 1972 Mitsuishi et al.. 264/290 T both f DOmigheim; Dietmar 3,739,056 6/1973 Evans et al 264/290 T Wandel, Offenbach am Main, all of Germany Primary ExaminerRobert F. White [73] Assignee: Zimmer Aktiengesellschaft, Assistant ExaminerJames B. Lowe Frankfurt, Germany Attorney, Agent, or FirmMolinare, Allegretti, Newitt Wt 22 Filed: Aug. 1, 1974 &

21 Appl. No.: 493,557

Related us. Application Data [571 ABSTRACT [63] Continuation 295,166: 1972 Improved stretching process for polyester cables abandoned wherein the penultimate roller of an inlet roller mechanism is immersed in abath maintained at a tempera- Forelgn Apphcatlon Pnoflty Data ture of 65C and the last roller of the mechanism Oct. 6, 1971 Germany 2149793 is higher than the penultimate roller and is maintained at a temperature 3I8C higher than the immersion U-S- Cl- Further the angle between vertical and the cable [5 Int. Cl. as it rises to the last roller is less than The resul. Field of Search 264/290 T, 210 F, DIG. 73, tant cables have a low percentage unstretched fibers 264/290 290 and, as a consequence, have a low percentage dyeing defects. [56] References Cited UNITED STATES PATENTS 2/1956 Calton 264/290 T 8 Claims, 1 Drawing Figure 1 PROCESS FOR STRETCHING A CABLE OF POLYESTER THREADS This is a continuation, of application Ser. No. 295,166, filed Oct. 5, 1972 now abandoned.

BACKGROUND OF THE INVENTION The invention relates to a process for stretching a cable of polyester threads, especially a cable of polyethylene terephthalate, between an inlet roller mechanism and a first stretching roller mechanism, in which the cable is conducted, within the inlet roller mechanism, through an immersion bath maintained at a tem perature between 40 and 65C.

It is known that the stretching of polyester threads is facilitated by using elevated temperatures. The heat action can take place through contacting the threads with heated plates, rollers, prongs or by passing the threads through a tempering bath. While uniform stretching of individual threads, or thread bundles generally presents no problem when they have low layer density, the uniform heating and stretching of thread cables having a high layer density is difficult. Staple fibers produced from unevenly stretched cables have the disadvantage that the insufficiently stretched fiber components, through their lesser molecular orientation, dye deeper and lead to colored textile surface structures having an unacceptable appearance.

The weight proportion deep-dyeing defects, which can be determined by sorting and weighing out, is, therefore, an important, characteristic value of a polyester fiber.

In order to remedy this defect as much as possible, thread cables, to obtain uniform tempering, are frequently heated to the stretching temperature with the aid of water baths. If the stretching zone is located in the water bath, this method of stretching leads to good textile physical values, particularly with respect to a low deep-dyeing defect component. The acceleration of the cable, however, causes considerable water to be carried along with the cable which, without influencing the stretching, is difficult to retain in the bath. The preliminary tempering, therefore, has already been arranged within the inlet roller mechanism for the stretching zone. Thus, in US. Pat. No. 3,557,273 there is illustrated a stretching process in which the yarn is V acted on with water directly before the stretching zone,

and the stretched thread does not pass through the immersion bath. In this process stretching takes place on staggered stretching prongs, on which the water is removed by the sharp deflection of the yarn. This process works for yarns of little density and at high stretching speeds but is not suited for thread cables of high density. Furthermore, the stretching temperature cannot be controlled at the unheated stretching prongs. In [1.5. Pat. No. 3,567,817 there is illustrated an immersion bath arranged Within the inlet roller mechanism to the stretching zone. This bath principally serves to swell the cable. To achieve a uniform cable temperature, the bath cooperates, further, with a cooling stage. This cooling stage consists of five or nine tempered rollers arranged on the outlet side of the bath. The inlet roller mechanism is, accordingly, rather expensive aside from the fact that the stretching itself also takes place in a bath. This results in the same problems, as previously mentioned, in the bath. Finally, in German published patent application DAS 1,193,198 there is illustrated wtretching polyester thread cables by the arrangement of an immersion bath within the inlet roller mechanism. Here, too, on the outlet side of the tempered bath there are engaged a number of tempered rollers to maintain the temperature of the cable and to promote the swelling process, before the cable enters a second, warmer bath, in which the stretching takes place. The disadvantages of this process are the same as those of the process illustrated in U.S. Pat. No. 3,567,817.

Underyling the invention is the problem of avoiding the disadvantages of the known processes and, in particular, of achieving a uniform stretching of cables having a high spinning denier, i.e. with over 1,000,000 den., with use of high stretching speeds of up to about 200 m/min without difficulty. Finally, the expenditure in apparatus for the solution of this problem should be kept as low as possible.

SUMMARY OF THE INVENTION The process, accordingly, proceeds from the stretching of a cable of polyester threads between an inlet roller mechanism and a first stretching roller mechanism, in which the stretchingpoint is formed at the last roller of the inlet roller mechanism. The process of this invention is characterized in that the cable, on going around the penultimate roller of the inlet roller mechanism passes through an immersion bath maintained at 40 to 65C and, the last roller of the inlet roller mechanism has a temperature that is 3 to 18C, preferably 5 to 12C, higher than the immersion bath. Further, the last roller is positioned higher than the penultimate roller and the angle between vertical and cable as it rises from the penultimate roller to the last roller is less than 55.

Accordingly, the cable is heated by the immersion bath to the desired stretching temperature only closely before the stretching point which is formed at the last roller of the inlet roller mechanism, The staying or residence time of the heated cable between the immersion bath and the beginning of the stretching is short.

As a result, there takes place virtually no inhomogeneous, superficial cooling of the cable up to the stretching point, which cannot be sufficiently prevented by interposed heated rollers. A further advantage of this process lies in that the precrystallization or the onset of an energy favored molecular state in the thread cable is prevented, thereby facilitating stretching. Further, the immersion bath can contain finish-containing water. Because of the sufficiently steep upward direction of the cable as it is drawn from the immersion bath, a large part of the water carried along with the cable runs by itself, back into the immersion bath. A further position of the water is squeezed out automatically in the passage of the cable around the last roller of the inlet roller mechanism. In this manner, the drag-water contained on the stretched cable is kept small, even in the case of high entry speeds. Preferably the angle between perpendicular and the cable rise between the last two rollers is chosen smaller than 30. The proportion of deep-dyeing defects (i.e. unstretched places) amounts, in the cable stretched according to the invention, to a maximum of 0.03 percent by weight.

Preferably the staying or residence time of the cable between the exit from the immersion bath and the commencement of the stretching at the last roller is chosen to be less than 3 sec.

When higher entry speeds are used, it is expedient to lengthen the path length of the cable in the immersion bath in order to achieve a uniform, thorough warming.

This can be accomplished with the aid of a deflection roller which is immersed in the lengthened bath.

Further, according to this invention the cable is heated in the first, stretch roller mechanism to a temperature between 30 and 85C, and preferably between 40 and 65C and is further stretched or after stretched between the first stretching roller mechanism and a subsequent second stretching roller mechanism positioned after the first mechanism. Through this after-stretching, the weight component of unstretched places in the cable is again reduced by a power of ten, i.e., to only 0.001 0.005 percent. The tensile strength of the final,'after-stretched cable lies between 4 and 7 g/den., depending on the exact stretching ratio applied and the molecular weight of the polyester used.

Preferably the cable, before entry into the inlet roller mechanism, is conducted through a moistening bath to swell the cable and the water carried along from this path is squeezed out so that the cable has a water content of less than 40 percent by weight before it enters the immersion bath. The moistening bath is filled with finish-containing water, whose temperature lies between 25 and 40C. Preferably, the water carried along from the moistening bath is squeezed out of the cable to a water content of less than 25 percent by weight. The squeezing out of the water from the cable is expediently accomplished with the aid of a squeeze roller which interacts with one of the first rollers of the inlet roller mechanism.

stretching of the cable in particular at temperatures between l 10 and 200C and preferably in a steam atmosphere.

DESCRIPTION OF DRAWING The invention is explained in detail by reference to the attached schematic drawing of an installation for the execution of the process of the invention.

A polyester thread cable is first conducted through a wetting bath 1 which contains a finish-containing water The wet cable then enters the inlet roller mechanism 2, consisting of seven rollers. At the second roller of mechanism 2, the water content of the cable is appreciably reduced by a squeeze roller 3. The next-tolast roller 5 of the inlet roller mechanism 2 is immersed in a bath 4, which is filled with tempered, finish containing water. The uniformly tempered thread cable runs from the roller 5 at a very acute angle to perpendicular upward over the tempered roller 6. From roller 6, the cable is drawn off with the aid of a first stretching roller mechanism 8 at a speed which is a multiple of the inlet speed of the cable. Between the last roller 6 of the inlet roller mechanism 2 and the stretching roller mechanism 8 there is positioned a first stretching field --7, in which the first cable stretching takes place. As illustrated in the drawings, the stretching in the field 7 is performed in the absence of the addition of water. The stretching roller mechanism 8 is followed by a second stretching roller mechanism 11. Between the two mechanisms the cable passes through a steam chamber 9, in which after-stretching takes place. The draw-off speed of the second stretching roller mechanism 11 is greater than that of the first stretching roller mechanism 8, so that between the two mechanisms, there is formed a second stretching field 10. The after-stretch achieved in field l0 contributes considerably to the improvement of the textile physical properties, especially to the lowering of the deep-dyeing defect component.

EXAMPLE In the installation represented in the attached schematic drawing, a polyethylene terephthalate thread cable with a limit viscosity (i.e. intrinsic viscosity) of 0.41 (measured in a solvent of 60 parts phenol, 40 parts tetrachlorethane, at a temperature of 25C) and a spinning denier of 2,000,000 den., consisting of 160,000 capillaries, was subjected to a stretching. After passing through the moistening bath, which consisted of finishcontaining water at a temperature of 35C, the cable was conducted over the inlet roller mechanism. With the aid of the squeeze roller mounted on the second roller the water carried along with the cable was removed to a residual moisture content of 25 percent by weight. The cable was then conducted through an immersion bath at the sixth roller as well as over the heated seventh roller, which is heated to a temperature of 65C to achieve a uniform thorough heating to the stretching temperature. The immersion bath was filled with finish-containing water and had a temperature of 58C. The peripheral speed of the inlet roller mechanism was 35 m/min and the application density of the cable was 56,000 den/cm. The cable was drawn off by means of the first stretching roller mechanism with a stretching ratio of 1:3.8 and the rollers of the first stretch roller mechanism had a temperature of 55C. Thereupon there followed an after-stretching in the ratio of 1:1.2 in a second stretching field, in which the cable was heated with the aid of a steam chamber having an inside temperature of C.

Under the process conditions, it was possible to achieve a faultless stretching operation. The cable obtained had a tensile strength of 4.3 g/den. and only 0.003 percent by weight components having unstretched places. In a cable taken after the first stretching field the proportion of unstretched places still amounted to 0.03 percent by weight.

With omission of the immersion bath provided according to the invention at the sixth roller of the inlet roller mechanism, despite after-stretching, there was measured an abrupt increase of the proportion of unstretched places to 0.6 percent by weight.

The process according to the present invention is suited for producing polyester fibers, especially low-pill polyester staple fibers with a very low proportion of unstretched places. Preferably, the starting material is a low-molecular polyester material. The process is not, however, restricted to this material, but extends to all forms of execution that fall under the appended claims.

We claim:

1. In a process for stretching a cable of polyester threads, between an inlet roller mechanism comprising a plurality of rollers and a first stretching roller mechanism, in which the stretching point is formed at the last roller of the inlet roller mechanism the improvement which comprises:

a. passing the cable while on the penultimate roller of the inlet roller mechanism through an immersion bath maintained at a temperature of 40 to 65C;

b. maintaining the last roller of the inlet roller mechanism at a temperature 3 to 18C higher than the immersion bath;

c. positioning the last roller higher than the penultimate roller with the angle between vertical and the cable as it rises from the penultimate roller to the last roller being less than 55 to remove fluid from the immersion bath on the cable;

d. maintaining a short residence time of less than 3 seconds for the cable between the exit point of the cable from the immersion bath and the beginning of the stretching of the cable at the last roller and,

e. stretching the cable in a stretching zone in the absence of the addition of water at a ratio of 1:25 to 1:6 to produce a cable with a low percentage unstretched fibers.

2. An improvement according to claim 1, wherein the cable is heated in the first stretching roller mechanism to a temperature between 30 and 85C, and is afterstretched between the fist stretching roller mechanism and a subsequent, second stretching roller mechanism.

3. An improvement according to claim 2, wherein the cable is after-stretched at a temperature between 1 10 and 200C.

4. An improvement according to claim 2, wherein the cable is heated to a temperature between 40 and 65C.

5. An improvement according to claim 1, wherein the cable, before entering the inlet roller mechanism is passed through a moistening bath to produce a cable containing water and the water carried along with the cable from said bath is removed by squeezing, before the cable enters the immersion bath, to provide a cable having a water content of less than 40 percent by weight.

6. An improvement according to claim 1, wherein the cable is subsequently stretched in a second stretching zone in the ratio of 121.1 to 1:20.

7. An improvement according to claim 1, wherein said polyester is polyethylene terephthalate.

8. An improvement according to claim 1, wherein the temperature of the last roller is 5 to 12C higher than the temperature of the immersion bath. 

1. IN A PROCESS FOR STRETCHING A CABLE OF POLYESTER THREADS, BETWEEN AN INLET ROLLER MECHANISM COMPRISING A PLURALITY OF ROLLERS AND FIRST STRETCHING ROLLER MECHANISM, IN WHICH THE STRETCHING POINT IS FORMED AT THE LAST ROLLER OF THE INLET ROLLER MECHANISM THE IMPROVEMENT WHICH COMPRISES: A. A PASSING THE CABLE WHILE ON THE PENULTIMATE ROLLER OF THE INLET ROLLER MECHANISM THROUGH IMMERSION BATH MAINTAINED AT A TEMPERATURE OF 40* TO 65*C: B. MAINTAINING THE LAST ROLLER OF THE INLET ROLLER MECHANISM BATH: AT A TEMPERATURE 3* TO 18*C HIGHER THAN HE IMMERSION C. POSITIONING THE LAST ROLLER HIGHER THAN THE PENULTIMATE ROLLER WITH THE ANGLE BETWEEN VERTICAL AND THE CABLE AS IT PRISES FROM THE PENULTIMATE ROLLER TO THE LAST ROLLER BEING LESS THAN 55* TO REMOVE FLUID ROM THE IMMERSION BATH ON THE CABLE: D. MAINTAINING A SHORT RESIDENCE TIME OF LESS THAN 3 SECONDS FOR THE CABLE BETWEEN THE EXIT POINT OF THE CABLE FROM THE IMMERSION BATH AND THE BEGINNING OF THE STRETCHING OF THE CABLE AT THE LAST ROLLER AND E. STRETCHING THE CABLE IN A STRETCHING ZONE IN THE ABSENCE OF THE ADDITION OF WATER AT A RATIO OF 1:25 TO 1:6 TO PRODUCE A CABLE WITH A LOW PERCENTAGE UNSTRETCHED FIBRES.
 2. An improvement according to claim 1, wherein the cable is heated in the first stretching roller mechanism to a temperature between 30* and 85*C, and is after-stretched between the fist stretching roller mechanism and a subsequent, second stretching roller mechanism.
 3. An improvement according to claim 2, wherein the cable is after-stretched at a temperature between 110* and 200*C.
 4. An improvement according to claim 2, wherein the cable is heated to a temperature between 40* and 65*C.
 5. An improvement according to claim 1, wherein the cable, before entering the inlet roller mechanism is passed through a moistening bath to produce a cable containing water and the water carried along with the cable from said bath is removed by squeezing, before the cable enters the immersion bath, to provide a cable having a water content of less than 40 percent by weight.
 6. An improvement according to claim 1, wherein the cable is subsequently stretched in a second stretching zone in the ratio of 1:1.1 to 1:2.0.
 7. An improvement according to claim 1, wherein said polyester is polyethylene terephthalate.
 8. An improvement according to claim 1, wherein the temperature of the last roller is 5* to 12*C higher than the temperature of the immersion bath. 